path.c: move some code out of strbuf_git_path_submodule()

refs is learning to avoid path rewriting that is done by
strbuf_git_path_submodule(). Factor out this code so it could be reused
by refs_* functions.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

path.c

@@ -471,39 +471,19 @@ const char *worktree_git_path(const struct worktree *wt, const char *fmt, ...)
 }
 
 /* Returns 0 on success, negative on failure. */
-#define SUBMODULE_PATH_ERR_NOT_CONFIGURED -1
 static int do_submodule_path(struct strbuf *buf, const char *path,
 			     const char *fmt, va_list args)
 {
-	const char *git_dir;
 	struct strbuf git_submodule_common_dir = STRBUF_INIT;
 	struct strbuf git_submodule_dir = STRBUF_INIT;
-	const struct submodule *sub;
-	int err = 0;
+	int ret;
 
-	strbuf_addstr(buf, path);
-	strbuf_complete(buf, '/');
-	strbuf_addstr(buf, ".git");
-
-	git_dir = read_gitfile(buf->buf);
-	if (git_dir) {
-		strbuf_reset(buf);
-		strbuf_addstr(buf, git_dir);
-	}
-	if (!is_git_directory(buf->buf)) {
-		gitmodules_config();
-		sub = submodule_from_path(null_sha1, path);
-		if (!sub) {
-			err = SUBMODULE_PATH_ERR_NOT_CONFIGURED;
-			goto cleanup;
-		}
-		strbuf_reset(buf);
-		strbuf_git_path(buf, "%s/%s", "modules", sub->name);
-	}
-
-	strbuf_addch(buf, '/');
-	strbuf_addbuf(&git_submodule_dir, buf);
+	ret = submodule_to_gitdir(&git_submodule_dir, path);
+	if (ret)
+		goto cleanup;
 
+	strbuf_complete(&git_submodule_dir, '/');
+	strbuf_addbuf(buf, &git_submodule_dir);
 	strbuf_vaddf(buf, fmt, args);
 
 	if (get_common_dir_noenv(&git_submodule_common_dir, git_submodule_dir.buf))
@@ -514,8 +494,7 @@ static int do_submodule_path(struct strbuf *buf, const char *path,
 cleanup:
 	strbuf_release(&git_submodule_dir);
 	strbuf_release(&git_submodule_common_dir);
-
-	return err;
+	return ret;
 }
 
 char *git_pathdup_submodule(const char *path, const char *fmt, ...)

submodule.c

@@ -1596,3 +1596,34 @@ const char *get_superproject_working_tree(void)
 
 	return ret;
 }
+
+int submodule_to_gitdir(struct strbuf *buf, const char *submodule)
+{
+	const struct submodule *sub;
+	const char *git_dir;
+	int ret = 0;
+
+	strbuf_reset(buf);
+	strbuf_addstr(buf, submodule);
+	strbuf_complete(buf, '/');
+	strbuf_addstr(buf, ".git");
+
+	git_dir = read_gitfile(buf->buf);
+	if (git_dir) {
+		strbuf_reset(buf);
+		strbuf_addstr(buf, git_dir);
+	}
+	if (!is_git_directory(buf->buf)) {
+		gitmodules_config();
+		sub = submodule_from_path(null_sha1, submodule);
+		if (!sub) {
+			ret = -1;
+			goto cleanup;
+		}
+		strbuf_reset(buf);
+		strbuf_git_path(buf, "%s/%s", "modules", sub->name);
+	}
+
+cleanup:
+	return ret;
+}

submodule.h

@@ -81,6 +81,12 @@ extern int push_unpushed_submodules(struct sha1_array *commits,
 				    int dry_run);
 extern void connect_work_tree_and_git_dir(const char *work_tree, const char *git_dir);
 extern int parallel_submodules(void);
+/*
+ * Given a submodule path (as in the index), return the repository
+ * path of that submodule in 'buf'. Return -1 on error or when the
+ * submodule is not initialized.
+ */
+int submodule_to_gitdir(struct strbuf *buf, const char *submodule);
 
 /*
  * Prepare the "env_array" parameter of a "struct child_process" for executing